How early should I start drafting individual defensive players?

Passing
Passing Yards (PY) 0.04
TD Pass (PTD) 5
50+ yard TD pass bonus (PTD50) 3
Interceptions Thrown (INT) -2
2pt Passing Conversion (2PC) 2 300-399 yard passing game (P300) 5
400+ yard passing game (P400) 5

Rushing
Rushing Yards (RY) 0.1
Every 10 rush attempts (RA10) 2
TD Rush (RTD) 7
50+ yard TD rush bonus (RTD50) 5
2pt Rushing Conversion (2PR) 2
100-199 yard rushing game (RY100) 5
200+ yard rushing game (RY200) 5

Receiving
Receiving Yards (REY) 0.1
Each reception (REC) 1
TD Reception (RETD) 7
50+ yard TD rec bonus (RETD50) 5
2pt Receiving Conversion (2PRE) 2
100-199 yard receiving game (REY100) 5
200+ yard receiving game (REY200) 5

Miscellaneous
Kickoff Return Yards (KR) 0.04 Punt Return Yards (PR) 0.04
Kickoff Return TD (KRTD) 7 Punt Return TD (PRTD) 7
Fumble Recovered for TD (FTD) 7 Total Fumbles Lost (FUML) -2
Interception Return TD (INTTD) 15 Fumble Return TD (FRTD) 15
Blocked Punt or FG return for TD (BLKKRTD) 15
Kicking
Each PAT Made (PAT) 1 FG Made (0-39 yards) (FG0) 3
FG Made (40-49 yards) (FG40) 4 FG Made (50+ yards) (FG50) 5
FG Missed (0-39 yards) (FGM0) -2 FG Missed (40-49 yards) (FGM40) -1

Defensive Players
1/2 Sack (HALFSK) 2.5
Blocked Punt, PAT or FG (BLKK) 6
Each Interception (INT) 6
Each Fumble Recovered (FR) 6
Each Fumble Forced (FF) 6
Each Safety (SF) 10
Assisted Tackles (TKA) 0.5
Solo Tackles (TKS) 1
Stuffs (SF) 3
Passes Defensed (PD) 2

Looks like defensive players can put up a boatload of points. I'd go as early as the 8th round if you want to make sure you land a Kuechly or Willis.